Cleaning solution for temporary adhesive for substrates, substrate cleaning method, and cleaning method for support or substrate

ABSTRACT

A cleaning solution for temporary adhesive for substrates contains: tetrabutylammonium fluoride; dimethyl sulfoxide; and a liquid compound having a solubility parameter of 8.0 or more and 10.0 or less and having a heteroatom. The tetrabutylammonium fluoride is preferably contained at a content of 1 mass % or more and 15 mass % or less in 100 mass % of a total of the tetrabutylammonium fluoride, the dimethyl sulfoxide, and the liquid compound. The dimethyl sulfoxide is preferably contained at a content of 5 mass % or more and 30 mass % or less in 100 mass % of a total of the tetrabutylammonium fluoride, the dimethyl sulfoxide, and the liquid compound.

FIELD

The present invention relates to a cleaning solution for temporaryadhesive for substrates, a substrate cleaning method, and a cleaningmethod for a support or a substrate.

BACKGROUND

Three-dimensional semiconductor mounting has become essential for ahigher density and a larger capacity. The three-dimensional mountingtechnique is a semiconductor production technique for thinning onesemiconductor chip and then connecting the chip to another chip by athrough silicon via (TSV) to form a multilayer. To realize thistechnique, steps of grinding a non-circuit-forming surface (alsoreferred to as “back surface”, herein) of a substrate on which asemiconductor circuit has been formed to thin the substrate, and thenforming an electrode including a TSV on the back surface are required.Conventionally, in the step of grinding the back surface of a siliconsubstrate, a protective tape for the back surface is attached to a sideopposite to the surface to be ground to prevent the wafer from breakingduring grinding. However, this tape uses an organic resin film as thebase material, which has flexibility, but insufficient strength and heatresistance. Thus, it is not suited to the step of forming a TSV orforming a wiring layer on the back surface.

In this context, a system has been proposed in which a semiconductorsubstrate is bonded to a support made of silicon, glass, or the likewith an adhesive layer interposed therebetween, to sufficientlywithstand the steps of grinding the back surface and forming a TSV andan electrode on the back surface. In this system, the adhesive layerused for bonding the substrate to the support is important. The adhesivelayer requires a sufficient durability to bond the substrate to thesupport without gaps and to withstand subsequent steps. Furthermore, theability to easily separate a thin wafer from the support finally isrequired. Herein, the adhesive layer is also referred to as a “temporaryadhesive layer” because it is finally separated.

After the support is separated, a part of the temporary adhesive layermay remain on a front surface of the substrate on which thesemiconductor circuit has been formed. Generally, such a remainingtemporary adhesive layer is cleaned with a cleaning solution to beremoved. Patent Literature 1 describes such a cleaning solution, thatis, a detergent composition used for cleaning the substrate frontsurface. The detergent composition contains (A) quaternary ammoniumsalt: 0.1 to 2.0 mass %, (B) water: 0.1 to 4.0 mass %, and (C) anorganic solvent: 94.0 to 99.8 mass %.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Laid-open No.    2015-7217

SUMMARY Technical Problem

However, the cleaning solution described in Patent Literature 1 has roomfor improvement in detergency for the temporary adhesive layer remainingon the substrate front surface.

The present invention was made in view of the above-described situation,and it is an object thereof to provide a cleaning solution havingexcellent detergency for a temporary adhesive layer remaining on asubstrate front surface.

Solution to Problem

To solve the above problem and to achieve the above objection, acleaning solution for temporary adhesive for substrates according to oneaspect of the invention includes tetrabutylammonium fluoride; dimethylsulfoxide; and a liquid compound having a solubility parameter of 8.0 ormore and 10.0 or less and having a heteroatom.

It is preferable that the tetrabutylammonium fluoride is contained at acontent of 1 mass % or more and 15 mass % or less in 100 mass % of atotal of the tetrabutylammonium fluoride, the dimethyl sulfoxide, andthe liquid compound.

It is preferable that the dimethyl sulfoxide is contained at a contentof 5 mass % or more and 30 mass % or less in 100 mass % of a total ofthe tetrabutylammonium fluoride, the dimethyl sulfoxide, and the liquidcompound.

It is preferable that the liquid compound is a compound having a ketonegroup or an ester group.

A substrate cleaning method according to another aspect of the inventionincludes steps of: separating a support from a substrate laminateincluding the support, a temporary adhesive layer formed on the support,and a substrate laminated on the temporary adhesive layer and having afront surface on which a circuit is formed and that faces the temporaryadhesive layer; and cleaning and removing the temporary adhesive layerremaining on the substrate with the cleaning solution for temporaryadhesive for substrates.

A cleaning method for a support or a substrate according to stillanother aspect of the invention includes steps of: forming a temporaryadhesive layer on a support or a substrate; and cleaning and removing apart of the temporary adhesive layer with the cleaning solution fortemporary adhesive for substrates.

Advantageous Effects of Invention

According to the present invention, the cleaning solution havingexcellent detergency for the temporary adhesive layer remaining on thesubstrate front surface can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for describing a substrate laminate.

DESCRIPTION OF EMBODIMENTS

The present invention will now be described in detail.

<Cleaning Solution for Temporary Adhesive for Substrates>

A cleaning solution for temporary adhesive for substrates according toan embodiment contains tetrabutylammonium fluoride, dimethyl sulfoxide,and a liquid compound having a solubility parameter of 8.0 or more and10.0 or less and having a heteroatom.

To perform a step of grinding the back surface of a substrate on which asemiconductor circuit has been formed, for example, the substrate and asupport are bonded with a temporary adhesive layer including thetemporary adhesive for substrates interposed therebetween. Specifically,as the temporary adhesive for substrates, a silicone-based adhesive isused. After completing the step of grinding the back surface, forexample, when the support has been separated, a part of the temporaryadhesive for substrates that forms the temporary adhesive layer mayremain on the substrate front surface. The cleaning solution fortemporary adhesive for substrates according to the embodiment ispreferably used for cleaning such temporary adhesive for substratesremaining on the substrate front surface. When the cleaning solution fortemporary adhesive for substrates according to the embodiment is usedfor cleaning, the remaining temporary adhesive for substrates (i.e., thesilicone-based adhesive) can be sufficiently removed. This can beachieved because the tetrabutylammonium fluoride and the dimethylsulfoxide are used in combination in the cleaning solution for temporaryadhesive for substrates according to the embodiment. It should be notedthat the cleaning solution for temporary adhesive for substratesaccording to the embodiment can preferably clean not only the substratethat has been thinned by the step of grinding the back surface but alsothe temporary adhesive for substrates remaining on the substrate frontsurface.

The liquid compound contained in the cleaning solution has a solubilityparameter of 8.0 or more and 10.0 or less. The solubility parameter ispreferably 8.0 or more and 9.5 or less. Herein, the solubility parameter(SP value, δ) is a parameter defined in the regular solution theoryintroduced by Hildebrand and Scott. This solubility parameter isexpressed as δ=(ΔE/V)^(1/2)(cal/cm³)^(1/2), where V is the molecularvolume of a solvent and ΔE is a cohesive energy (evaporation energy).

The liquid compound has a heteroatom. Examples of the heteroatom includean oxygen atom. Specifically, the liquid compound is preferably acompound having a ketone group (—C(C═O)—) or an ester group(—O—C(C═O)—). The liquid compound is easily mixed with thesilicone-based adhesive and can sufficiently remove the silicone-basedadhesive because it has a solubility parameter within theabove-described range and has a specific heteroatom (e.g., theabove-described groups).

Examples of the liquid compound specifically include methyl isobutylketone (δ=8.4), methyl isopropyl ketone (δ=8.5), methyl n-propyl ketone(δ=8.7), methyl ethyl ketone (δ=9.3), cyclohexanone (δ=9.9), acetone(δ=10.0), isobutyl acetate (δ=8.3), n-butyl acetate (δ=8.5), ethylacetate (δ=9.1), and propylene glycol monomethyl ether acetate (δ=9.1).The liquid compound may be used alone, or may be used in combination oftwo or more kinds thereof. Among these, in respect of detergency for thesilicone-based adhesive, n-butyl acetate and propylene glycol monomethylether acetate are more preferable.

In the cleaning solution for temporary adhesive for substrates accordingto the embodiment, the tetrabutylammonium fluoride is preferablycontained at a content of 1 mass % or more and 15 mass % or less in 100mass % of a total of the tetrabutylammonium fluoride, the dimethylsulfoxide, and the liquid compound. The content is more preferably 3mass % or more and 15 mass % or less. When the tetrabutylammoniumfluoride is contained within the above-described range, thesilicone-based adhesive can be sufficiently removed. If the content isless than 1 mass %, cleaning may be insufficient. If the content exceeds15 mass %, the substrate may be corroded.

In the cleaning solution for temporary adhesive for substrates accordingto the embodiment, the dimethyl sulfoxide is preferably contained at acontent of 5 mass % or more and 30 mass % or less in 100 mass % of atotal of the tetrabutylammonium fluoride, the dimethyl sulfoxide, andthe liquid compound. The content is more preferably 10 mass % or moreand 30 mass % or less. When the dimethyl sulfoxide is contained withinthe above-described range, the silicone-based adhesive can besufficiently removed. If the content is less than 5 mass %, cleaning maybe insufficient. If the content exceeds 30 mass %, the substrate may becorroded.

The cleaning solution for temporary adhesive for substrates according tothe embodiment may contain, as other components, a surfactant, achelating agent, an antioxidant, an anticorrosive, a defoaming agent, apH adjuster, and an aromatic compound. Specific examples of thesurfactant include polyether-based nonionic surfactants although theymay be any of nonionic, anionic, and cationic ones. The other componentsmay be used alone, or may be used in combination of two or more kindsthereof. The other components when being added, for example, may becontained each in an amount of 0.01 part by mass or more and 10 parts bymass or less with respect to 100 parts by mass of a total of thetetrabutylammonium fluoride, the dimethyl sulfoxide, and the liquidcompound.

A method of preparing the cleaning solution for temporary adhesive forsubstrates according to the embodiment is not limited to a particularone. The cleaning solution for temporary adhesive for substratesaccording to the embodiment is obtained by mixing the above-describedcomponents, for example. The order in which the components are mixed isnot limited to a particular one.

The flash point of the cleaning solution for temporary adhesive forsubstrates according to the embodiment is preferably 21° C. or higher.When the flash point is within the above-described range, cleaning withthe above-described cleaning solution can be performed safely.

<Substrate Cleaning Method>

A substrate cleaning method according to the embodiment includes stepsof: separating a support from a substrate laminate including thesupport, a temporary adhesive layer formed on the support, and asubstrate laminated on the temporary adhesive layer and having a frontsurface on which a circuit is formed and that faces the temporaryadhesive layer; and cleaning and removing the temporary adhesive layerremaining on the substrate with the above-described cleaning solutionfor temporary adhesive for substrates. When the above-described cleaningsolution for temporary adhesive for substrates is used, the temporaryadhesive layer remaining on the substrate (i.e., out of thesilicone-based adhesive forming the temporary adhesive layer, thesilicone-based adhesive remaining on the substrate) can be sufficientlyremoved.

Specifically, the substrate cleaning method according to the embodimentincludes steps of: (a) preparing a substrate laminate; (b) grinding orpolishing the back surface of a substrate in the substrate laminate; (c)processing the back surface of the substrate; (d) separating a supportfrom the substrate laminate; and (e) cleaning the front surface of thesubstrate with the cleaning solution for temporary adhesive forsubstrates. Herein, a case will be described in which the temporaryadhesive layer is formed by a cured layer (A) obtained by curing anuncured composition layer of thermosetting organopolysiloxane.

[Step (a)]

The step (a) is a step of preparing a substrate laminate. FIG. 1 is adiagram for presenting the substrate laminate. FIG. 1 illustrates asectional view of a substrate laminate 10, and the substrate laminate 10includes a support 1, a temporary adhesive layer 2 formed on the support1, and a substrate 3 laminated on the temporary adhesive layer 2 andhaving a front surface on which a circuit is formed and that faces thetemporary adhesive layer 2.

Specifically, at step (a), a circuit-forming surface of the substratethat has the circuit-forming surface on the front surface and anon-circuit-forming surface on the back surface is bonded to the supportwith the temporary adhesive layer (cured layer (A)) interposedtherebetween. More specifically, step (a) includes steps of: (a-1)laminating, on the support, an uncured composition layer ofthermosetting organopolysiloxane and thermoplastic organopolysiloxane asthe silicone-based adhesive; (a-2) bonding the support and the substratewith the uncured composition layer interposed therebetween; and (a-3)heat curing the uncured composition layer to obtain a cured layer (A).Herein, step (a-1) may be step (a-1′) of laminating the uncuredcomposition layer on the substrate, and step (a-2) may be step (a-2′) ofbonding the substrate and the support with the uncured composition layerobtained at step (a-1′) interposed therebetween.

At step (a-1) or (a-1′), when the uncured composition layer islaminated, a film of an uncured composition may be used. Alternatively,a solution of an uncured composition may be laminated by spin coating,slit coating, spray coating, or the like. The solution is laminatedpreferably by spin coating. In this case, generally, after spin coating,prebaking is performed at a temperature of 80° C. or higher and 250° C.or lower, and preferably at 100° C. or higher and 230° C. or lower,depending on the volatile conditions of the solvent contained in theuncured composition.

At step (a-1) or (a-1′), the uncured composition layer is preferablyformed so as to have a film thickness of 10 μm or more and 150 μm orless. When the film thickness is 10 μm or more, the substrate and thesupport can be bonded without gaps to sufficiently withstand thegrinding step described later. If the thickness is 150 μm or less, theresin can be prevented from deforming in a heat treatment step such as aTSV formation step described later, and can be put to practical use.

At step (a-2) or (a-2′), the substrate is uniformly compressed underreduced pressure at a temperature of, for example, 40° C. or higher and250° C. or lower, and more preferably 60° C. or higher and 200° C. orlower, whereby the support and the substrate are bonded. For thebonding, a commercially available wafer-bonding apparatus such as EVG520IS and EVG850 TB (product name) manufactured by EV Group, XBC300(product name) manufactured by SUSS MicroTec AG, and Synapse V (productname) manufactured by Tokyo Electron Ltd. is used.

At step (a-3), the uncured composition layer is heated at a temperatureof, for example, 120° C. or higher and 250° C. or lower, and preferably140° C. or higher and 200° C. or lower, for 10 minutes or more and 4hours or less, and preferably for 30 minutes or more and 2 hours orless, whereby the thermosetting organopolysiloxane is cured.

The substrate used at step (a) is typically a semiconductor wafer.Examples of the semiconductor wafer include a silicon wafer, a germaniumwafer, a gallium-arsenide wafer, a gallium-phosphide wafer, and agallium-arsenide-aluminum wafer. The thickness of the wafer istypically, but is not limited to, 600 μm or more and 800 μm or less, andmore typically 625 μm or more and 775 μm or less.

Examples of the support used at step (a) include a substrate such as asilicon wafer, a glass plate, and a quartz wafer.

Hereinafter, the uncured composition of thermosetting organopolysiloxanein particular and the cured layer (A) containing the cured productthereof to be used at step (a) will be described in more detail.

(Uncured Composition)

The uncured composition contains for example: (A-1) organopolysiloxanehaving two or more alkenyl groups per molecule; (A-2)organohydrogenpolysiloxane having two or more silicon-bonded hydrogenatoms (Si—H groups) per molecule; and (A-3) a platinum-based catalyst.Herein, the mole ratio of the Si—H group in the component (A-2) to thealkenyl group in the component (A-1) is 0.3 or more and 10 or less. Theuncured composition may also contain (A-4) an organic solvent or (A-5) areaction controlling agent.

The component (A-1) is organopolysiloxane having two or more alkenylgroups per molecule. The component (A-1) is, for example, linear orbranched diorganopolysiloxane having two or more alkenyl groups permolecule, or organopolysiloxane having a resin structure having asiloxane unit (Q unit) expressed as a SiO_(4/2) unit. The component(A-1) is preferably organopolysiloxane containing the alkenyl groups at0.6 mol % or more and 9 mol % or less per molecule (mole of alkenylgroup/mole of Si).

Specifically, the organopolysiloxane described above is represented bythe following formulae (1), (2), and (3). These may be used alone, ormay be used in combination of two or more kinds thereof.

R⁷ _((3-a))X_(a)SiO—(R⁷XSiO)_(m)—(R⁷ ₂SiO)_(n)—SiR⁷ _((3-a))X_(a)  (1)

R⁷ ₂(HO)SiO—(R⁷XSiO)_(p+2)—(R⁷ ₂SiO)_(q)—SiR⁷ ₂(OH)  (2)

(SiO_(4/2))_(b)(R⁷ ₃SiO_(1/2))_(c)(R⁷ _((3-e))X_(e)SiO_(1/2))_(d)  (3)

In the above formulae, R⁷ is independently a monovalent hydrocarbongroup having no aliphatic unsaturated bond; X is independently amonovalent organic group containing an alkenyl group; “a” is an integerof 0 to 3; m, n are such numbers that 2a+m allows the content of thealkenyl group to be 0.6 mol % or more and 9 mol % or less per molecule;p, q are such numbers that p+2 allows the content of the alkenyl groupto be 0.6 mol % or more and 9 mol % or less per molecule; e isindependently an integer of 1 to 3; and b, c, d are such numbers that(c+d)/b is 0.3 to 3.0 and that d/(b+c+d) is 0.01 to 0.6.

In the above formulae, R⁷ is preferably a monovalent hydrocarbon grouphaving 1 to 10 carbon atoms. Specifically, examples of R⁷ include: alkylgroups such as a methyl group, an ethyl group, a propyl group, and abutyl group; cycloalkyl groups such as a cyclohexyl group; and arylgroups such as a phenyl group and a tolyl group. Among these, alkylgroups and a phenyl group are preferable.

X is preferably an organic group having 2 to 10 carbon atoms. Examplesof X include: alkenyl groups such as a vinyl group, an allyl group, ahexenyl group, and an octenyl group; (meth)acryloylalkyl groups such asan acryloylpropyl group, an acryloylmethyl group, and amethacryloylpropyl group; (meth)acryloxyalkyl groups such as anacryloxypropyl group, an acryloxymethyl group, a methacryloxypropylgroup, and a methacryloxymethyl group; a cyclohexenylethyl group; and avinyloxypropyl group. Among these, a vinyl group is industriallypreferable.

In the above formula (1), when “a” is 1 to 3, terminals of the molecularchain are blocked with alkenyl groups. The reaction can be completedwithin a short time by the alkenyl groups with good reactivity at theterminals of the molecular chain. Furthermore, a=1 is industriallypreferred in view of the cost. This alkenyl group-containingdiorganopolysiloxane is preferably in an oil state or a crude rubberstate.

The above formula (3) represents organopolysiloxane having a resinstructure. In the above formula (3), e=1 is industrially preferred inview of the cost. The product of the average of e and d/(b+c+d) ispreferably 0.02 to 1.50, and more preferably 0.03 to 1.0. Thisorganopolysiloxane having a resin structure may be used as a solutiondissolved in an organic solvent.

The component (A-2) is a crosslinker, which isorganohydrogenpolysiloxane having at least two, more preferably three ormore, silicon-bonded hydrogen atoms (Si—H groups) per molecule. Thisorganohydrogenpolysiloxane has a linear, branched, or cyclic structure.

The viscosity of the component (A-2) at 25° C. is preferably 1 mPa·s ormore and 5,000 mPa·s or less, and more preferably 5 mPa·s or more and500 mPa·s or less. This organohydrogenpolysiloxane may be used alone, ormay be used in combination of two kinds thereof.

The component (A-2) is desired to be blended in such an amount that themole ratio of the Si—H group in the component (A-2) to the alkenyl groupin the component (A-1) (Si—H group/alkenyl group) is preferably 0.3 ormore and 10 or less, and more preferably 1.0 or more and 8.0 or less.When this mole ratio is 0.3 or more, the crosslinking density is notexcessively reduced, and the uncured composition layer can be preferablycured. When the mole ratio is 10 or less, the crosslinking density isnot excessively increased, and sufficient viscosity and tackiness can beachieved. In addition, the mole ratio of 10 or less can make theavailable time of the uncured composition longer.

The component (A-3) is a platinum-based catalyst (i.e., platinum groupmetal catalyst). Examples of the platinum-based catalyst includechloroplatinic acid, an alcohol solution of chloroplatinic acid, areaction product of chloroplatinic acid with alcohol, a reaction productof chloroplatinic acid with an olefin compound, and a reaction productof chloroplatinic acid with a vinyl group-containing siloxane. Theplatinum-based catalyst may be used alone, or may be used in combinationof two or more kinds thereof.

The component (A-3) is desired to be blended in an amount of preferably1 ppm or more and 5,000 ppm or less, and more preferably 5 ppm or moreand 2,000 ppm or less in terms of (the mass of) platinum with respect tothe total of the component (A-1) and the component (A-2). When theamount is 1 ppm or more, curability of the uncured composition layer isless likely to decrease. Thus, decrease in crosslinking density and alsodecrease in holding force can be suppressed. The amount of 5,000 ppm orless can make the available time of the uncured composition longer.

The component (A-4) is an organic solvent. The organic solvent is notlimited to a particular one if it can dissolve the component of theuncured composition. Examples of the organic solvent include hydrocarbonsolvents such as pentane, hexane, cyclohexane, isooctane, nonane,decane, p-menthane, pinene, isododecane, and limonene, and asilicone-based solvent. The organic solvent may be used alone, or may beused in combination of two or more kinds thereof.

When the component (A-4) is used, the component (A-4) is desired to beblended in an amount of preferably 10 parts by mass or more and 900parts by mass or less, more preferably 25 parts by mass or more and 400parts by mass or less, and still more preferably 40 parts by mass ormore and 300 parts by mass or less with respect to 100 parts by mass ofa total of the component (A-1) and the component (A-2).

The component (A-5) is a reaction controlling agent. With the reactioncontrolling agent, when the uncured composition is prepared or theuncured composition is applied to the base, the uncured composition canbe prevented from thickening or gelling before heat curing.

Examples of the reaction controlling agent include:3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol,3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol,3-methyl-3-trimethylsiloxy-1-butyne,3-methyl-3-trimethylsiloxy-1-pentyne,3,5-dimethyl-3-trimethylsiloxy-1-hexyne,1-ethynyl-1-trimethylsiloxycyclohexane,bis(2,2-dimethyl-3-butynoxy)dimethylsilane,1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and1,1,3,3-tetramethyl-1,3-divinyldisiloxane. Among these,1-ethynylcyclohexanol and 3-methyl-1-butyn-3-ol are preferable. Thereaction controlling agent may be used alone, or may be used incombination of two or more kinds thereof.

When the component (A-5) is used, the component (A-5) is desired to beblended in an amount of preferably 0.01 part by mass or more and 8.0parts by mass or less, and more preferably 0.05 part by mass or more and2.0 parts by mass or less with respect to 100 parts by mass of a totalof the component (A-1) and the component (A-2). When the amount is 8.0parts by mass or less, curability of the uncured composition layer isless likely to decrease. When the amount is 0.01 part by mass or more,the effect of controlling the reaction can be sufficiently exhibited.

The uncured composition may further contain other components. Examplesof the components include: a filler such as silica; unreactivepolyorganosiloxanes such as polydimethyl siloxane andpolydimethyldiphenyl siloxane; antioxidants of a phenol type, a quinonetype, an amine type, a phosphorus type, a phosphite type, a sulfur type,a thioether type, or other types; photo stabilizers of a triazole type,a benzophenone type, or other types; flame retardants of a phosphoricacid ester type, a halogen type, a phosphorus type, an antimony type, orother types; and antistatic agents such as a cationic activator, ananionic activator, and a nonionic activator. The other components may beused alone, or may be used in combination of two or more kinds thereof.

The other components are blended within a range not impairing the objectof the present invention. For example, when a filler is used to increasethe heat resistance, the filler is preferably blended in an amount of 50parts by mass or less with respect to 100 parts by mass of a total ofthe component (A-1) and the component (A-2).

(Cured Layer (A))

The cured layer (A) is obtained by heat curing the uncured compositionlayer, and contains a cured product of the uncured composition asdescribed above.

The cured layer (A) laminated on the support, when being interfaciallypeeled from the support, exhibits a peeling force of, for example, 10mN/25 mm or more and 500 mN/25 mm or less, preferably 30 mN/25 mm ormore and 500 mN/25 mm or less, and more preferably 50 mN/25 mm or moreand 200 mN/25 mm or less. The peeling force herein is a peeling forceobtained in a 180° peel test in which a test piece having a width of 25mm is pulled up at 5 mm/s to be peeled. When it is 10 mN/25 mm or more,separation during a processing step and the like described later can beprevented. When it is 500 mN/25 mm or less, the cured layer (A) can beeasily removed from the support.

The cured layer (A) laminated on the substrate, when being interfaciallypeeled from the substrate, exhibits a peeling force of, for example, 50mN/25 mm or more and 1,000 mN/25 mm or less, preferably 70 mN/25 mm ormore and 1,000 mN/25 mm or less, and more preferably 80 mN/25 mm or moreand 500 mN/25 mm or less. Herein, the peeling force is a peeling forceobtained in a 180° peel test in which a test piece having a width of 25mm is pulled up at 5 mm/s to be peeled. When it is 50 mN/25 mm or more,separation during a processing step and the like described later can beprevented. Separation is less likely to occur even though a hightemperature process in particular. When the peeling force is 1,000 mN/25mm or less, the cured layer (A) can be removed from the substrate by atape.

The cured product contained in the cured layer (A) preferably contains asiloxane unit (M unit) expressed as R¹R²R³SiO_(1/2) at 0.001 mol % ormore and 60.000 mol % or less, a siloxane unit (D unit) expressed asR⁴R⁵SiO_(2/2) at 10.000 mol % or more and 99.999 mol % or less, asiloxane unit (T unit) expressed as R⁶SiO_(3/2) at 0.000 mol % or moreand 0.005 mol % or less, and a siloxane unit (Q unit) expressed asSiO_(4/2) at 0.000 mol % or more and 60.000 mol % or less. It is morepreferable that the cured product contain the M unit at 0.001 mol % ormore and 35.000 mol % or less, the D unit at 30.000 mol % or more and99.999 mol % or less, the T unit at 0.000 mol % more and 0.001 mol % orless, and the Q unit at 0.000 mol % or more and 50.000 mol % or less.

Herein, R¹, R², R³, R⁴, R⁵ and R⁶ are organic substituents, which areunsubstituted or substituted monovalent hydrocarbon groups. Thesehydrocarbon groups each preferably have 1 to 10 carbon atoms.Specifically, examples of the hydrocarbon groups include: alkyl groupssuch as a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, a t-butyl group, an n-pentyl group, acyclopentyl group, and an n-hexyl group; cycloalkyl groups such as acyclohexyl group; aryl groups such as a phenyl group and a tolyl group;and groups in which a part or all of the hydrogen atoms of the abovegroups are substituted by halogen atoms. Among these, a methyl group anda phenyl group are preferable.

The storage elastic modulus of the cured layer (A) at 25° C. ispreferably 1×10⁶ Pa or more and 1×10⁹ Pa or less. When the storageelastic modulus is within this range, the substrate can withstand thegrinding step described later, and warpage thereof can be reduced. Thus,a problem such as poor fit to a device at a step is less likely tooccur.

[Step (b)]

Step (b) is a step of grinding or polishing the back surface of thesubstrate in the substrate laminate. At step (b), the back surface(non-circuit-forming surface) of the substrate bonded to the support isground or polished. By this step, the thickness of the substrate isreduced. The thickness of the thinned substrate is typically 5 μm ormore and 300 μm or lees, and more typically 10 μm or more and 100 μm orless. The technique for grinding is not limited to a particular one, andknown techniques may be used. The grinding is preferably performed whilewater is fed to the substrate and a grinding wheel (e.g., diamond) forcooling. Examples of an apparatus for grinding the back surface of thesubstrate include DAG-810 (product name) manufactured by DISCO Co., Ltd.The back surface of the substrate may be subjected to CMP polishing.

[Step (c)]

Step (c) is a step of processing the back surface of the substrate. Atstep (c), the back surface (non-circuit-forming surface) of thesubstrate that has been thinned by grinding the back surface orpolishing the back surface at step (b) is processed. This step includesvarious processes applied in the wafer level. Examples of this stepinclude electrode formation, metal wiring formation, and protective filmformation. More specifically, the examples include well-known processessuch as metal sputtering for forming electrodes or the like, wet etchingfor etching a sputtered metal layer, a process in which a resist isapplied and subjected to exposure and development to form a pattern usedas a mask for metal wiring formation, resist peeling, dry etching,plating with metal, silicon etching for forming a TSV, and formation ofan oxide film on a silicon surface. The examples also include a processin which the wafer thinned by dicing or the like is cut into chips.

[Step (d)]

Step (d) is a step of separating the support from the substratelaminate. At step (d), the support is separated from the substratelaminate processed at step (c). This separating step is generallyperformed under relatively low temperature conditions from roomtemperature to about 60° C. This step can be performed by horizontallyfixing one of the substrate and the support of the substrate laminateand lifting the other at a certain angle with respect to the horizontaldirection. Alternatively, a protective film may be bonded to the groundsurface of the substrate, and then the substrate together with theprotective film may be separated by peeling.

Specifically, this peeling includes steps of: (d-1) bonding a dicingtape to the processed surface of the processed substrate; (d-2)attaching a dicing tape surface by vacuum suction to a suction surface;(e-3) separating the support from the substrate by peeling-off at atemperature of the suction surface in the range of 10° C. or higher and100° C. or lower. In this case, the support can be easily separated fromthe substrate, and the subsequent dicing step can be easily performed.

By this separating step, the cured layer (A) together with the supportis separated from the substrate laminate, whereby only the substrate isobtained. Other than this case, there is a case in which only thesupport is separated from the substrate laminate, whereby the substrateon which the cured layer (A) is laminated is obtained. In the lattercase, the cured layer (A) is further separated from the substrate bytape peeling, whereby only the substrate is obtained. As a tape to beused for tape peeling, a tape using silicone adhesive is preferable. Forexample, polyester film adhesive tapes No. 646S and No. 648 manufacturedby Teraoka Seisakusho Co., Ltd. are preferably used.

[Step (e)]

Step (e) is a step of cleaning the front surface of the substrate withthe above-described cleaning solution for temporary adhesive forsubstrates. At step (e), with the cleaning solution for temporaryadhesive for substrates, the cured layer (A) (the cured product of theuncured composition) remaining on the front surface (circuit-formingsurface) of the substrate is cleaned and removed. By this step, thecured layer (A) that partially remains on the front surface of thesubstrate even after the support and the cured layer (A) have beenseparated at step (d) can be sufficiently removed. This substrate(thinned wafer) is preferably used subsequently for a three-dimensionalsemiconductor mounting process.

This cleaning may be performed with the substrate being immersed in thecleaning solution for temporary adhesive for substrates. This immersingtime is approximately, for example, 10 seconds or more and 30 minutes orless, and preferably 30 seconds or more and 10 minutes or less.Alternatively, the cleaning may be performed with the substrate beingsprayed with the cleaning solution for temporary adhesive forsubstrates. Furthermore, the cleaning may be performed by paddling withthe cleaning solution for temporary adhesive for substrates, and shakingor ultrasonic cleaning may be performed. The temperature for thecleaning is, for example, 10° C. or higher and 50° C. or lower, andpreferably 20° C. or higher and 40° C. or lower.

Herein, the substrate after being cleaned may be rinsed with water oralcohol and dried.

In the substrate cleaning method according to the embodiment describedabove, at step (a), the uncured composition layer of thermosettingorganopolysiloxane is cured to form the cured layer (A) as the temporaryadhesive layer. Alternatively, as the temporary adhesive layer, which isnot limited to the cured layer (A), a temporary adhesive layer obtainedfrom another silicone-based adhesive may be used. Although the curedlayer (A) has a single layer, two or more temporary adhesive layers maybe formed. The temporary adhesive layer on the cured layer (A) may be,although not limited to, silicone-based, acrylic, or phenolic, forexample. In addition, a layer containing organopolysiloxane having afunction other than the temporary adhesive layer may be formed betweenthe support and the substrate. Specifically, examples of the othersilicone-based adhesive include silicone-based adhesives described inInternational Publication No. WO2015/115060, Japanese Patent ApplicationLaid-open No. 2012-144616, Japanese Patent Application Laid-open No.2014-131004. In any cases, if the cleaning solution for temporaryadhesive for substrates is used, the temporary adhesive layer remainingon the substrate front surface can be sufficiently removed.

In the substrate cleaning method according to the embodiment, at step(d), the support may be separated as described above. However, thisseparation of the support may be performed by photo peeling, heatpeeling, solvent peeling, or mechanical peeling. In any cases, if thecleaning solution for temporary adhesive for substrates is used, thetemporary adhesive layer remaining on the substrate front surface can besufficiently removed.

In photo peeling, generally, at step (a), a separation layer is formedin the substrate laminate in advance. Specifically, the separation layeris formed between the support and the temporary adhesive layer. Theseparation layer is formed of, for example, a known material thatabsorbs light radiated through the support to deteriorate, such as,although not limited to, carbon and an aromatic hydrocarbon compound.The deterioration means a state in which the separation layer is brokenby a slight external force or a state in which adhesive strength betweenthe separation layer and a layer that is in contact therewith hasdecreased. Subsequently, step (b) and step (c) are performed on thesubstrate laminate having the separation layer as described above.Subsequently, at step (d), the support is separated from the substratelaminate by photo peeling. Herein, light is radiated on substratelaminate through the support from a known laser. In this case, a laserconfigured to radiate light having a wavelength that can cause materialsforming the separation layer to deteriorate may be appropriatelyselected. By this radiation, the separation layer deteriorates, and thesupport is separated. Subsequently, at step (e), with the cleaningsolution for temporary adhesive for substrates, the front surface of thesubstrate obtained by the photo peeling is cleaned.

In heat peeling, generally, at step (a), a silicone-based adhesive theadhesive strength of which is reduced by heating is used to form atemporary adhesive layer in advance. Subsequently, step (b) and step (c)are performed on the substrate laminate having this temporary adhesivelayer as described above. Subsequently, at step (d), the support isseparated from the substrate laminate by heat peeling. Subsequently, atstep (e), with the cleaning solution for temporary adhesive forsubstrates, the front surface of the substrate obtained by the heatpeeling is cleaned.

In solvent peeling, at step (d), the support is separated from thesubstrate laminate by solvent peeling. In this case, a solvent that candissolve the silicone-based adhesive forming the temporary adhesivelayer may be appropriately selected, and examples thereof includesolvents of a hydrocarbon type having 4 to 20 carbon atoms, an aromatictype, and an ether type. Subsequently, at step (e), with the cleaningsolution for temporary adhesive for substrates, the front surface of thesubstrate obtained by the solvent peeling is cleaned.

In the substrate cleaning method according to the embodiment describedabove, at step (a), the whole surface of the circuit-forming surface ofthe substrate is bonded to the support with the temporary adhesive layerobtained from the uncured composition of one type interposedtherebetween. Instead of this, to adjust the bonding strength betweenthe support and the substrate, a first temporary adhesive layer may beformed on a part of the substrate front surface, and a second temporaryadhesive layer may be formed on the remaining part of the substratefront surface. In other words, the whole surface of the substrate frontsurface may be covered by the first temporary adhesive layer and thesecond temporary adhesive layer. Silicone-based adhesives that aresuitable for the respective layers to obtain a desired bonding strengthare selected to form the first temporary adhesive layer and the secondtemporary adhesive layer.

Furthermore, in this case, when the temporary adhesive layer is formed,the above-described cleaning solution for temporary adhesive forsubstrates is preferably used. To begin with, the first temporaryadhesive layer is formed on the whole surface of the substrate.Subsequently, with the cleaning solution for temporary adhesive forsubstrates, an unnecessary part of the first temporary adhesive layer (apart on which the second temporary adhesive layer is to be formed) issubjected to an edge-cut treatment. When the cleaning solution fortemporary adhesive for substrates is used, the unnecessary part of thefirst temporary adhesive layer can be cleanly removed from thesubstrate. On this edge-cut part, the second temporary adhesive layer isformed. The circuit-forming surface of the substrate is then bonded tothe support with the first temporary adhesive layer and the secondtemporary adhesive layer interposed therebetween. Subsequently, at step(b), the back surface of the substrate in the substrate laminate havingthe first temporary adhesive layer and the second temporary adhesivelayer is ground or polished. In the foregoing, the temporary adhesivelayer is formed on the substrate. However, the temporary adhesive layermay be formed on the support. Specifically, as described above, acleaning method for a support or a substrate according to the embodimentincludes steps of: forming the temporary adhesive layer on the supportor the substrate; and cleaning and removing a part of the temporaryadhesive layer with the above-described cleaning solution for temporaryadhesive for substrates.

The present invention is not limited to the above-described embodiment.Those configured by appropriately combining the respectiveconstitutional elements described above are also included in the presentinvention. Furthermore, additional effects or modifications can beeasily derived by the skilled person. Thus, a wider aspect of thepresent invention is not limited to the above-described embodiment, andvarious changes may be made.

EXAMPLES

Hereinafter, the present invention will be specifically described withreference to Examples, but the present invention is not limited to theseExamples.

<Cleaning Solution for Temporary Adhesive for Substrates>

Example 1-1

Tetrabutylammonium fluoride and dimethyl sulfoxide were added topropylene glycol monomethyl ether acetate, and the resulting mixture wasstirred at room temperature to obtain a cleaning solution (1-1). In thecleaning solution (1-1), the tetrabutylammonium fluoride was dissolved.Here, the cleaning solution was prepared such that thetetrabutylammonium fluoride was contained at a content of 10 mass % in100 mass % of a total of the tetrabutylammonium fluoride, the dimethylsulfoxide, and the propylene glycol monomethyl ether acetate. Thecleaning solution was also prepared such that the dimethyl sulfoxide wascontained at a content of 20 mass % in 100 mass % of a total of thetetrabutylammonium fluoride, the dimethyl sulfoxide, and the propyleneglycol monomethyl ether acetate.

Example 1-2

The same preparation was performed as in Example 1-1 except that butylacetate was used instead of the propylene glycol monomethyl etheracetate, whereby a cleaning solution (1-2) was obtained.

Example 1-3

The same preparation was performed as in Example 1-1 except thatcleaning solution was prepared such that the tetrabutylammonium fluorideis contained at 5 mass % in 100 mass % of a total of thetetrabutylammonium fluoride, the dimethyl sulfoxide, and the propyleneglycol monomethyl ether acetate, whereby a cleaning solution (1-3) wasobtained.

Example 1-4

Tetrabutylammonium fluoride and dimethyl sulfoxide were added topropylene glycol monomethyl ether acetate, and the resulting mixture wasstirred at room temperature to obtain a cleaning solution (1-4). In thecleaning solution (1-4), the tetrabutylammonium fluoride was dissolved.Here, the cleaning solution was prepared such that thetetrabutylammonium fluoride is contained at a content of 10 mass % in100 mass % of a total of the tetrabutylammonium fluoride, the dimethylsulfoxide, and the propylene glycol monomethyl ether acetate. Thecleaning solution was also prepared such that the dimethyl sulfoxide iscontained at a content of 10 mass % in 100 mass % of a total of thetetrabutylammonium fluoride, the dimethyl sulfoxide, and the propyleneglycol monomethyl ether acetate.

Comparative Example 1-1

Dimethyl sulfoxide was added to propylene glycol monomethyl etheracetate, and the resulting mixture was stirred at room temperature toobtain a cleaning solution (1-5). Here, the cleaning solution wasprepared such that the dimethyl sulfoxide is contained at a content of20 mass % in 100 mass % of a total of the dimethyl sulfoxide and thepropylene glycol monomethyl ether acetate.

<Cleaning of Substrate>

Example 2-1

To begin with, a resin solution was prepared as follows.

A solution consisting of 100 parts by mass of polydimethylsiloxanehaving 2.5 mol % of vinyl groups at molecular side chains with a numberaverage molecular weight (Mn) of 30,000 and 200 parts by mass of toluenewas prepared. To this solution, 40 parts by mass oforganohydrogenpolysiloxane represented by formula (M-1) below and 0.7part by mass of ethynylcyclohexanol were added, and then mixed.Furthermore, 0.2 part by mass of a platinum catalyst CAT-PL-5(manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto, andthe resulting mixture was filtered through a 0.2-μm membrane filter toobtain a resin solution. In the resin solution, the mole ratio of Si—Hgroups of organohydrogenpolysiloxane having Si—H groups to alkenylgroups in organopolysiloxane having alkenyl groups was 1.1.

Subsequently, a substrate was cleaned as follows.

[Step (a)]

A substrate laminate was prepared. Specifically, on a 200-mm glass wafer(thickness: 700 μm) as a support, an uncured composition layer(thickness: 35 μm) was laminated by spin coating with the resin solutionand then heating with a hot plate at 50° C. for 3 minutes. Subsequently,a 200-mm diameter silicon wafer (thickness: 725 μm) as a substrate, onthe entire front surface of which copper posts having a height of 10 μmand a diameter of 40 μm were formed, was bonded to the support such thatthe copper post surface faces the uncured composition layer surface. Thebonding was performed by a wafer-bonding apparatus (EVG520 IS (productname) manufactured by EV Group). The bonding was performed at a bondingtemperature of 50° C., under a chamber internal pressure of 10⁻³ mbar orless during bonding, with a load of 10 kN. After the bonding, the bondedsubstrate was heated with an oven at 200° C. for 2 hours, and theuncured composition layer was cured, and was cooled to room temperature.Through these processes, a substrate laminate was obtained.

[Step (b)]

Subsequently, the back surface of the substrate in the substratelaminate was ground. Specifically, the back surface of the silicon waferwas ground by a grinder (DAG810 (product name) manufactured by DISCOCo., Ltd.) with a diamond grinding wheel. It was ground to a finalsubstrate thickness of 50 μm.

[Step (c)]

Subsequently, as a step of processing the back surface of the substrate,a heating step was performed in a simulated condition. Specifically, thesubstrate laminate for which the back surface had been ground was heatedon a hot plate at 260° C. for 10 minutes.

[Step (d)]

Subsequently, the support was separated from the substrate laminate.Specifically, a dicing tape was bonded to the back surface(non-circuit-forming surface) of the silicon wafer with a dicing frame,and this dicing tape surface was set to a suction plate by vacuumsuction. Subsequently, one point of the glass wafer was lifted bytweezers at room temperature, whereby the glass wafer was separated.Subsequently, a polyester film adhesive tape No. 648 manufactured byTeraoka Seisakusho Co., Ltd. was bonded to a temporary adhesive layerthat had been exposed at the front surface, and tape peeling wasperformed. In this manner, the temporary adhesive layer was removed fromthe silicon wafer.

[Step (e)]

Subsequently, with the cleaning solution (1-1), the front surface of thesubstrate was cleaned. Specifically, the silicon wafer was immersed inthe cleaning solution (1-1) for 10 minutes, and was then dried at roomtemperature.

Example 2-2 to Example 2-4 and Comparative Example 2-1

The same processes were performed as in Example 2-1 except that thecleaning solution (1-2) to the cleaning solution (1-5) were used insteadof the cleaning solution (1-1), whereby the substrate was cleaned.

<Evaluation Method>

As a result of measuring by XPS the amount of Si elements that werepresent on the front surface (circuit-forming surface) of the substratethat had undergone step (d) was measured, the Si content was 23%.Herein, in the Si content, Si derived from a silicon substrate isomitted.

The amount of Si elements that were present on the front surface(circuit-forming surface) of the substrate that had undergone step (e)was also measured by XPS.

When the Si content after the cleaning is less than 5%, the cleaningsolution can be considered to have excellent detergency for thetemporary adhesive layer remaining on the front surface of thesubstrate.

Herein, the XPS was performed with an X-ray photoelectron spectroscopyanalyzer (PHI Quantera SXM (product name) manufactured by ULVAC-PHI,Inc.). Specifically, it was performed with monochromatized AlKα for theX-ray source at an output of 25 W (15 kV, 100-μm diameter), aphotoelectron take-off angle of 45°, a pass energy of 55.0 eV, and astep resolution of 0.05 eV. The analysis area was φ500 μm.

<Evaluation Results>

When substrate cleaning methods as in Examples 2-1 to 2-4 were performedwith the cleaning solutions obtained in Examples 1-1 to 1-4, theremaining amount of Si was less than 3% in all cases. In contrast, whensubstrate cleaning as in Comparative Example 2-1 was performed with thecleaning solution obtained in Comparative Example 1-1 that does notsatisfy the requirements of the present invention, the remaining amountof Si remaining after the cleaning was 23%, and thus excellentdetergency could not be obtained.

It should be noted that the present invention is not limited to theabove-described embodiment. The embodiment is merely exemplification,and any examples that have substantially the same feature anddemonstrate the same functions and effects as those in the technicalconcept described in claims of the present invention are included in thetechnical scope of the present invention.

REFERENCE SIGNS LIST

-   -   1 support    -   2 temporary adhesive layer (cured layer (A))    -   3 substrate    -   10 substrate laminate

1. A cleaning solution for temporary adhesive for substrates, thecleaning solution comprising: tetrabutylammonium fluoride; dimethylsulfoxide; and a liquid compound having a solubility parameter of 8.0 ormore and 10.0 or less and having a heteroatom.
 2. The cleaning solutionfor temporary adhesive for substrates according to claim 1, wherein thetetrabutylammonium fluoride is contained at a content of 1 mass % ormore and 15 mass % or less in 100 mass % of a total of thetetrabutylammonium fluoride, the dimethyl sulfoxide, and the liquidcompound.
 3. The cleaning solution for temporary adhesive for substratesaccording to claim 1, wherein the dimethyl sulfoxide is contained at acontent of 5 mass % or more and 30 mass % or less in 100 mass % of atotal of the tetrabutylammonium fluoride, the dimethyl sulfoxide, andthe liquid compound.
 4. The cleaning solution for temporary adhesive forsubstrates according to claim 1, wherein the liquid compound is acompound having a ketone group or an ester group.
 5. A substratecleaning method comprising steps of: separating a support from asubstrate laminate including the support, a temporary adhesive layerformed on the support, and a substrate laminated on the temporaryadhesive layer and having a front surface on which a circuit is formedand that faces the temporary adhesive layer; and cleaning and removingthe temporary adhesive layer remaining on the substrate with thecleaning solution for temporary adhesive for substrates according toclaim
 1. 6. A cleaning method for a support or a substrate comprisingsteps of: forming a temporary adhesive layer on a support or asubstrate; and cleaning and removing a part of the temporary adhesivelayer with the cleaning solution for temporary adhesive for substratesaccording to claim 1.